更新时间:2023-02-06 09:12:35
你需要这样做 -
SELECT C.ClassId, C.ClassName, count(S.StudentId) AS studentCount FROM CLASSES C LEFT JOIN STUDENTS S ON (C.ClassId=S.ClassId) GROUP BY C.ClassId, C.ClassName
从另一个表中选择计数到结果行中的每一行